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1984 190 E
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72 Posts
MY aux fan goes on and off at will. I changed my relay and sensor. Before nothing would go on. sometimes it stays on and I remove the relay. but I do not mind it going on when I am in Los Angeles traffic. I had a bad overheating problem when I first got my Baby Benz. But now it does not overheat unless I am sitting in traffic.
 

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Premium Member
W-1-2-3 Go!
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16,161 Posts
I've replaced the following:

1. Blue insulator sensor at engine block (close to valve cover)
2. Pre-resistor relay
3. Auxiliary fan relays (2)
4. Thermostat (79C)
5. Radiator (replaced prior to ownership, in 2008, with Nissens unit)

The auxiliary fans come on once in a while. My mechanic soldered some diodes/resistors on the blue insulator pins so the fans come on earlier, before 100C (maybe 95C). I don't mind this, because I just had the valves done (seals, guides, valves) and head gasket alongside this job.

I've got 2 new auxiliary fans waiting to be installed when the old ones go kaput. One has noisy bearing, the other seems okay.
 

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1984 190 E
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72 Posts
Good idea to place the diode/resistor at the temp sensor to drop the value and get that fan going sooner. gotta try it with different values myself. still want to make a cold start valve myself to save some cash. I just use a temp switch to hit a bit into the chamber and go.
 

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Registered
1992 190e 2.6
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254 Posts
Discussion Starter #5
I isntalled a fan switch on the head.

Unlike before the fans do not come in at cold start but should they be already on at this level



At what point should I consider it overheating?

Also, the fans do not come on at slow speed with AC on, though I may be low on freon.
 

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1984 190 E
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72 Posts
QuickSilver2 - That is the point where mine goes on too. The forum somewhere states the water will start to boil before the fans go on. I have not had any problems since I replaced the electronics stated in MBEIGE post. If you travel on the freeways here in California often, you could just put in a switch to turn it on and off but if you Benz runs at the temp on your picture. you will be fine. Also, My fans sometimes stay on so I just pull the relay in front of the fuse box when I am parked. put it back when I go. But it usually behaves fine. I think the pre-resistor is the culprit as all the rest are new and that one looked new when I pulled it from a wrecked 190.
 

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Registered
1992 190e 2.6
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254 Posts
Discussion Starter #7
Here is what I bought from AutoHausaz

"Radiator/Auxiliary Fan Switch; Blue Insulator with 2 Prong Connector; 130 Degree C"

Is this the right part? It seems it will come on at 130 degrees, yes?

Just to clarify, my fan doesn't come on even at the level pictured (but it comes on when I jump the switch on the ehad.
 

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1984 190 E
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72 Posts
Cooling Fan Sensor; Auxiliary Fan Switch; 212 Degree F part # 0065451424

relay listed as "Fuel Pump Relay; With 4 Pin Connector and 30 Amp Fuse" on Autohausaz part # 0015429619 goes in front of fuse box and is for the fan relay not the fuel pump relay. the difference is the four prong not five.
are what I bought there.
 

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Premium Member
W-1-2-3 Go!
Joined
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16,161 Posts
Here is what I bought from AutoHausaz

"Radiator/Auxiliary Fan Switch; Blue Insulator with 2 Prong Connector; 130 Degree C"

Is this the right part? It seems it will come on at 130 degrees, yes?

Just to clarify, my fan doesn't come on even at the level pictured (but it comes on when I jump the switch on the ehad.
This item triggers the fans to turn on when the vehicle is overheating. This item also renders the AC compressor inoperable to maximize cooling and minimize engine damage.

My mechanic added the resistor here, I don't know what numbers he used though, but the fans turn on at around 100C instead. Since my AC doesn't work I don't mind this modification yet. But when I get around to fixing it, cutting off the compressor too soon might cause the cabin to heat up too quick. For now, my setup works for me.

Freeway driving is fine. It's when you get stuck in traffic does the temperature go up slowly, the fans turn on, and it takes a few minutes idling to get the temperature to go back down to around 80 or 85C, about the range when the fans turn off.

The symptoms of creeping temp when idling are when the ambient temps are around 80 F.
 

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Registered
1984 190E 2.3 engine Automatic, 2002 C240 2.6 Automatic
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240 Posts
I dont worry about the temperature gauge moving up and down. Coolant under pressure boils at a higher temperature.

My aux fan doesent come on in normal traffic/heat. A/C doesent work at all, yet. The fan clutch does, as needed. I've replaced the water temp switches for both the fan clutch and the aux fan with new, and tested them in boiling water before they were installed. The aux fan system works fine if I ground the the connector to the switch. The car is not getting hot enough to engage this fan, as it is on the return water line from the radiator.

Notice where the red marks are on the temperature gauge. My engine temperature never gets anywhere near that mark, so I'm happy.

I dont try to re-engineer this car. I'm being sure that all systems are working at factory settings. My mechanic thinks I'm doing it right, as he is impressed at what I've done with this car since 2007.
 
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